linux-kernel - Re: [PATCH v6 1/7] mm/memcg: scanning_global_lru means mem_cgroup

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Message-ID: <20120326150429.GA22754@tiehlicka.suse.cz>
Date:	Mon, 26 Mar 2012 17:04:29 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Glauber Costa <glommer@...allels.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v6 1/7] mm/memcg: scanning_global_lru means
 mem_cgroup_disabled

[Adding Johannes to CC]

On Fri 23-03-12 01:56:16, Konstantin Khlebnikov wrote:
> From: Hugh Dickins <hughd@...gle.com>
> 
> Although one has to admire the skill with which it has been concealed,
> scanning_global_lru(mz) is actually just an interesting way to test
> mem_cgroup_disabled().  Too many developer hours have been wasted on
> confusing it with global_reclaim(): just use mem_cgroup_disabled().

Is this really correct?

> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Acked-by: Glauber Costa <glommer@...allels.com>
> ---
>  mm/vmscan.c |   18 ++++--------------
>  1 files changed, 4 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 49f15ef..c684f44 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
[...]
> @@ -1806,7 +1796,7 @@ static int inactive_anon_is_low(struct mem_cgroup_zone *mz)
>  	if (!total_swap_pages)
>  		return 0;
>  
> -	if (!scanning_global_lru(mz))
> +	if (!mem_cgroup_disabled())
>  		return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup,
>  						       mz->zone);

mem_cgroup_inactive_anon_is_low calculation is slightly different than
what we have for cgroup_disabled case. calculate_zone_inactive_ratio
considers _all_ present pages in the zone while memcg variant only
active+inactive.

>  
> @@ -1845,7 +1835,7 @@ static int inactive_file_is_low_global(struct zone *zone)
>   */
>  static int inactive_file_is_low(struct mem_cgroup_zone *mz)
>  {
> -	if (!scanning_global_lru(mz))
> +	if (!mem_cgroup_disabled())
>  		return mem_cgroup_inactive_file_is_low(mz->mem_cgroup,
>  						       mz->zone);
>  
> 
> --
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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